Eeeek! It's the old hag again!

Q.Relaxing in your easy chair, you're suddenly gripped by a powerful sense of terror without any ostensible cause. Worse, you can't move, as if paralyzed, and begin to sense an evil presence. Who or what has come to visit? –E. Roosevelt

A. It's the "Old Hag," as mentioned in various folklores, says Leonard George, in Alternative Realities. On occasion, the normal boundary between waking and sleeping blurs, giving rise to strange experiences, perhaps shuffling sounds, musty odors, hallucinations. In Newfoundlandic lore, there is the curious custom of "hagging"– supposedly if people say the Lord's Prayer backward while kneeling and call out "Hag, good Hag," their enemy will be visited by the Old Hag that night.

"Sleep paralysis" is the modern designation, where the normal paralysis that keeps a person from acting out dreams intrudes during sleep onset or awakening, says a spokesman at the University of Montreal Dream and Nightmare Laboratory. Fear follows and dream-like images can erupt. Transitions in and out of REM (dream) sleep seem the cause. Most of us will experience the Old Hag at least once.

So when it happens, try to move your eyes and blink, suggests the spokesman. Move your tongue or wiggle your toes. This may break the logjam. A noise may do it, or the paralysis may disappear spontaneously, no lasting harm done.

Q.What did the great Albert Einstein, not always with his "head in the clouds" over relativity theory (100 years old in 2005), know about rivers? –M. Twain

A. He was the first to suggest why so many of them pursue a winding and eventually looping course, such as Cleveland's 100-mile horseshoe Cuyahoga River (American Indian for "crooked"), says Simon Singh in Fermat's Enigma.

Einstein's insight: Once even a slight curve develops, faster currents along the outer bank will result in more erosion and a sharper bend. This will speed the outer current even more, and so on. All this bending will eventually lead to the river doubling back on itself, in effect short-circuiting its course. "At last the river will become straighter and the loop will be left to one side, forming an oxbow lake," Singh says.

A. In fact, they are, says University of Akron professor Alan N. Gent. In one test, the wear debris was caught in a vacuum cleaner following closely behind a car, revealing particles 10-100 microns in size, hardly visible, but still black and rubbery. These particles usually settle alongside the road and slowly degrade, disappearing as carbon dioxide gas within a matter of days or a few weeks.

The rubber itself is probably beneficial to the soil. But what about minor rubber compound constituents that don't easily vaporize, such as zinc, which may end up as a contaminant?

"It is not known at present whether this is a serious matter or too small a concentration to worry about," Gent says.

BTW, did you know that rubber got its name, circa 1880, from pencil erasers that rubbed the paper, with particles left behind, says Univ. of Akron chemical engineer J. Richard Elliott. With tires, the blackness comes from carbon black, 10-30 percent by weight; otherwise, the rubber is off- white or even pink, like an eraser.

The latest technology uses fillers of silica– not so black– for easier roll and greater tear resistance. Either way, the small tire particles simply join the organic roadway runoff of oil and gas, "erased" from view.